In textile yarn processing machines, particularly a two-for-one twister, a supply package of yarn is carried by a spindle assembly and the unprocessed yarn is drawn off from the supply package in an upward direction, introduced into the top of a yarn inlet tube and passed down through a yarn passageway through the spindle assembly and through the supply package of yarn and then radially outwardly from the spindle assembly. The yarn is then passed upwardly around the outside of the supply package where it forms a rotating balloon of yarn therearound. The yarn then passes through a thread guide eyelet positioned axially above the yarn entry tube. The yarn is processed by the spindle assembly in a well known manner to form a two-for-one twist therein. From the yarn guide eyelet, the yarn passes upwardly to a processed yarn take-up assembly which includes a cradle mechanism carrying a take-up package of yarn and means for selectively rotating the take-up package for winding of the processed yarn thereon.
In the event of yarn breakage, which normally occurs in the vicinity of the rotating baloon of yarn, one of the broken ends of yarn is normally wound onto the take-up package and is worked into the surface thereof. Continued rotation of the take-up package is stopped either manually or by conventional sensing mechanisms sensing the yarn breakage. Thereafter, in order to remedy this yarn breakage, it is necessary to bring together the broken ends of yarn from the take-up assembly and the spindle assembly, respectively, and knot these ends together.
For aiding in achieving this knotting operation, mechanisms are described in U.S. Pat. No. 3,975,893, issued Aug. 24, 1976, and assigned to the assignee of the present invention, for pneumatically threading a yarn end from the supply package through the spindle assembly so that the yarn end would be accessible from the spindle assembly for receipt by a knotter mechanism.
Also, apparatus is described in U.S. Pat. No. 3,478,504, issued Nov. 18, 1969, and assigned to the assignee of the present invention, which includes a self-propelled service trolley which can be run on rails along the outside of the machine for convenient positioning at a selected yarn processing station when a yarn break occurs. The service trolley carries a yarn transfer mechanism which includes an uncoiling roller for engaging the take-up package of processed yarn in the take-up assembly and rotating this take-up package in a direction opposite to the yarn take-up direction for unwinding the yarn. A suction duct is provided which has a knotting device therein and a mouth on one end for receipt of the broken end of yarn unwound from the take-up package and a mouth at the other end thereof for receiving the broken end of yarn from the spindle assembly, so that both ends of yarn may be carried through the suction duct to the knotting device for knotting the ends together. The suction duct is longitudinally slotted at the side facing the yarn processing station for removal of the yarn therefrom after knotting.
In this prior yarn transfer mechanism, there arises in the zone of the longitudinal slot in the suction duct considerable pressure losses resulting in a reduction in the suction force in the duct unless elaborate or expensive sealing strips are provided or the energy expended for such suction is raised to produce adequate suction to overcome such losses. Accordingly, problems have been presented with the construction and operation of the mechanism of this patent.
Additionally, German patent specification OS No. 22 10 469 and U.S. Pat. No. 3,628,320, disclose mechanisms for transferring yarn from a take-up package. However, these devices do not overcome the problems set forth above with respect to the apparatus of assignee's prior U.S. Pat. No. 3,478,504.